The film continues the story of the Jigsaw Killer's obsession with teaching people the value of their lives. Despite Jigsaw's death in the previous installment, the film focuses on his ability to manipulate people into continuing his work. The story follows Lieutenant Daniel Rigg being put through a series of tests in order to try to let go of his obsession with saving everyone, while at the same time attempting to save his partner.

The film was released in North America on October 26, 2007, to generally negative reviews from critics. Despite this, the film was a box office success, grossing $139 million worldwide.

Contents

A wax-coated microcassette is found in John Kramer's stomach during his autopsy, and reveals to Detective Mark Hoffman that the games will continue and he will still be tested. Elsewhere, two men - one with his eyes sewn shut, the other with his mouth sewn shut - awaken in a mausoleum, chained at the neck to a winch. The blinded man panics and activates the winch before attacking the muted man, who kills him in self-defense and uses a key from his collar to free himself.

Four days after Allison Kerry's death, a SWAT team led by Hoffman and Lieutenant Daniel Rigg find her body, and Hoffman warns Rigg against breaking through an unsecured door to reach her. The scene is also investigated by Peter Strahm and Lindsey Perez, Kerry's FBI contacts, who received a message and a key from her. Noting John and Amanda Young's physical limitations, Strahm speculates that a third accomplice was involved and soon becomes suspicious of Rigg, who has developed an obsession with saving people in the six months since the disappearance of detective Eric Matthews. That night, Rigg is attacked in his home; he awakens and watches a video from Jigsaw, which is where he learns that Eric is still alive and he has ninety minutes to save him, with Hoffman's life at risk as well. Meanwhile, he must play his own game in order to face and overcome his obsession.

Rigg finds a prostitute, named Brenda, bound to a chair in his living room, and accidentally activates the trap, which slowly tears her scalp off. He manages to free her, but kills her in self-defense when she attacks him with a knife in order to evade arrest. Rigg is then led to a motel and instructed to abduct the owner, Ivan Landsness, who Rigg later finds out is a serial rapist. He forces Ivan onto a bed, which requires Ivan to blind both of his eyes in order to escape. However, Ivan only blinds one of his eyes, and the trap dismembers him. Next, Rigg is led to a school, where he finds a married couple impaled by metal spikes: Rex, who has already died from blood loss; and his abused wife Morgan, who has remained alive at his expense by pulling the spikes from both of their bodies. Rigg pulls out the last spike and gives her a key to free herself. He then turns on a fire alarm and goes to the location of his final test.

The agents alternate between investigating the scenes and questioning Jill Tuck, John's ex-wife. Jill reveals John worked in civil engineering and property development, and that she miscarried her son Gideon after seven months when Cecil Adams, a drug addict, slammed a door into her stomach while robbing her health clinic. At the motel, the agents learn that the room was rented out to a lawyer named Art Blank, the survivor of the mausoleum trap, who vanished two weeks prior. Art is revealed to be the man overseeing the current game when he hands Eric a gun. At the school, the agents learn that all three victims, and Jill were Art's clients. Strahm and Perez find a puppet and a tape recorder in another room, which plays a cryptic message for Perez before its face explodes, sending shrapnel into her face. After Perez is hospitalized, Strahm furiously questions Jill. He learns how Kramer ended his work with Art after falling into his depression, and that Cecil became the first victim of John's "games". Strahm connects her story and a prior clue to the Gideon Meatpacking Plant, the location of Rigg's final test.

Strahm arrives after Rigg, but ends up following Jeff Denlon. After finding Jeff in the sickroom, Strahm shoots him in self-defense when Jeff demands his daughter back. Meanwhile, Art pulls out a device which will free them when the timer expires; if used before then, a pair of pincers will sever his spine. Rigg finds them and is shot by Eric as he breaks into the room with one second to spare, releasing two overhead ice blocks that swing down and crush Eric's head, killing him. Rigg shoots and kills Art, believing he is responsible for the game, only to learn from Art's tape recorder that his interference and continued obsession caused Eric's death. Hoffman, the actual accomplice, releases himself from the chair, but leaves Rigg to die. He then seals Strahm in the sickroom and leaves the plant. The scene then cuts to Hoffman at the morgue, revealing that John's autopsy took place after the events of the film.

In an interview with Bousman, he stated that the last work on Saw IV would happen in August to be able to have prints made.[6] At Comic Con 2007, it was revealed by Bousman and producer Mark Burg that the MPAA had given the film an NC-17 rating. They would have to figure out whether or not to cut the film to achieve an R rating or release it as an NC-17 film,[13] the former of which they accomplished.[14]

The film grossed $63,300,095 in the United States and an additional $71,228,814 internationally, bringing the theatrical total to $134,528,909.[16] It is Lionsgate's sixth highest-grossing film in the United States and Canada.[17]

Critical reception to Saw IV was negative. Rotten Tomatoes reports that 17% of critics gave the film a positive review, based upon 78 reviews, with an average score of 3.7 out of 10.[18] The Rotten Tomatoes consensus states: “Saw IV is more disturbing than compelling, with material already seen in the prior installments.” On Metacritic, the film has an average score of 36 out of 100, based on 16 reviews, indicating "Generally unfavorable reviews"[19]

Scott Schueller from the Los Angeles Times called it “a film as edgy as a rubber knife” and said that “if the terrible craft of Bousman's film doesn’t turn your stomach, the borderline pornographic violence will. It’s disconcerting to imagine anyone enjoying the vile filth splashing the screen.”[20] Frank Scheck from The Hollywood Reporter said “the famously inventive torture sequences here seem depleted of imagination”, but added that “it hasn’t yet jumped the shark like such predecessors as the Nightmare on Elm Street and Friday the 13th movies eventually did.”[21] Peter Hartlaub from The San Francisco Chronicle called it “the Syriana of slasher films, so complicated and circuitous that your only hope of understanding everything is to eat lots of fish the night before and then watch each of the previous films, in order, right before you enter the theater.”[22]James Berardinelli wrote that “Saw IV functions as a drawn-out, tedious epilogue to a series that began with an energetic bang three years ago with Saw, then progressively lost momentum, coherence, and intelligence with each successive annual installment.”[23]

A less negative review came from Jamie Russell from the BBC, who called it "deeply unsettling; just like a horror movie should be."[24] Linda Cook from Quad-City Times gave it a positive review and said "The twists and turns are deadly, the 'lessons' are taught once again, and we have the perfect setup for Saw V."[25]

The Unrated Director's Cut was released on January 22, 2008 in America and March 3, 2008 in the UK, on DVD and Blu-ray. The "Extreme Edition", which was released in the UK only, before the release of Saw V in October 2008[26][27] features a 95-minute running time of the film. This version of the film matches the unrated version released in the United States[28] (since the BBFC have to classify every film by law, the term 'unrated' is not permitted on UK home video releases).